1. Field of the Invention
The invention relates generally to an actuator to be used in a micro-electromechanical system, and more particularly to, an electromagnetic-type actuator for providing a parallel displacement to the surface of a microelectronic substrate.
2. Description of the Prior Art
An actuator which is the most important component in the micro-electromechanical system, has been implemented through a lot of driving principles. As one example, there are an electrostatic actuator using an electrostatic force between two different electrodes, a piezoelectric actuator using a piezoelectric material, a thermal actuator using thermal expansion of materials or thermal expansion of air contained within a limited space, an electromagnetic actuator using an electromagnetic force, and the like.
Many micro-electromechanical devices have been manufactured by means of above-mentioned driving principles. For example, there are a micro-gear, a micro-motor and a micro-machined device which can be moved or apply force, or the like. These micro-electromechanical devices can be applied to various applications. For example, they can be applied to an ultra fine fluid control device having a micro-pump, a valve or a mixer, an optical device having an optical switch, a shutter, or an attenuator, and an electrical device having a relay or an RF switch.
Of them, an electromagnetic-type actuator is driven using an electromagnetic force generated by means of coupling of a coil through which current flows and a magnetic substance. This electromagnetic-type actuator is advantageous in that it has relatively great displacement and force, and a rapid response speed. However, there are not so many cases that the electromagnetic actuator is applied to the micro-electromechanical system, compared to the micro actuator using other driving principle. The reason is that the electromagnetic-type actuator has many disadvantages such as complication of manufacturing process and difficulty of a fine displacement with its various advantages. In addition, the electromagnetic-type actuator has many complications in manufacturing process and requires a large number of masks, since a coil and a magnetic substance are used.
A typical example of a driving principle of the electromagnetic-type actuator includes U.S. Pat. No. 5,945,898 entitled ‘Magnetic Micro-actuator’ and issued Aug. 31, 1999, and U.S. Pat. No. 6,124,650 entitled ‘Non-Volatile MEMS Micro-Relays Using Magnetic Actuators’ and issued Sep. 26, 2000.
The U.S. Pat. No. 5,945,898 proposes a magnetic actuator in which a plate made of a magnetic substance stands up in a vertical direction by means of a magnetic field vertically generated in the electromagnetic plate. Further, the U.S. Pat. No. 6,124,650 proposes a structure in which a plurality of metal wires of a straight line is formed on a micro electronic substrate, a cantilever is formed at the side of the metal wire and the cantilever is floated on the metal wire. At this time, the magnetic substance is moved up and down depending on the direction of current flowing through the metal wire since the magnetic substance is formed on the cantilever. The micro cantilever is operated by the up and down movement of the cantilever.
Most actuators using the above electromagnetic force as the driving principle are manufactured as follows. A coil is first formed on an electromagnetic substrate. An empty space is then formed on the coil and a cantilever or a membrane is secondly formed. Next, a magnetic substance is formed on it. At this time, the two U.S. patents proposed above do not go beyond this range. This type of the electromagnetic-type micro-electromechanical actuator is basically limited to movement in a vertical direction to the electromagnetic plate.